Specialists at the Massachusetts Institute of Technology announced the establishment of an absolute record for the speed of data transfer from space to Earth. The shoebox-sized pilot plant transmitted information at a rate of 100 Gbps. At the next stage, the developers promise to double the transmission speed, which will provide scientific satellites with unprecedented communication channels in terms of speed.
Image Source: Lincoln Laboratory / MIT
SpaceX’s most expensive Starlink satellite internet plan provides a downlink at speeds up to 500 Mbps. The solution proposed by American developers is 200 times greater than the capabilities of Starlink. It looks incredible, but it’s all about the transmission medium – if Starlink communicates with a ground station via a radio channel, then the TeraByte InfraRed Delivery (TBIRD) system uses a laser beam for this.
Due to the higher frequency, the laser beam allows more data to be transmitted per unit of time. But this does not mean that the proposed method does not have shortcomings – there are plenty of them. The earth’s atmosphere distorts the signal – it introduces interference into it and leads to packet loss. Also, the laser must be extremely accurately directed to the receiver, which is not required for the radio beam. In the TBIRD project, MIT had to overcome all these technological barriers and more in order to create low-cost, high-performance laser satellite communication nodes.
A prototype laser transmitter with a fast storage, optical modem and optical amplifier was assembled from commercially available components, although a number of components had to be modified to work in a vacuum (for example, the absence of natural thermal convection simply melted optical fibers). The block weighing just over 11 kg (25 lb) was manufactured by Terran Orbital and placed on a NASA Ames Research Center cubesat chassis. A cubesat with a laser transmitter was launched into low Earth orbit at a height of 480 km in May 2022 by a SpaceX rocket.
The laser signal was received by a meter-long adaptive optics telescope at an optical ground station in California. During the experiments, the communication system showed a record communication speed of up to 100 Gbps. By the way, the team of engineers solved the problem of accurately aiming the laser at the receiver in a simple way – they abandoned the individual targeting mechanism. The laser guides the cubesat chassis to the receiver with the help of orientation motors. At the same time, the transmitter unit itself remains simple and compact, which was one of the objectives of the project.
In addition, the team also developed its own version of the automatic retransmission request (ARQ) protocol. If errors creep into the transmission, then the updated protocol over a slow outgoing communication channel does not request the repetition of the entire transmission, but only individual blocks with errors, which almost does not slow down the communication session.
“Going forward, we plan to take advantage of the additional capabilities of the TBIRD system, including an increase in speed to 200 gigabits per second, which will allow us to transfer more than 2 terabytes of data – the equivalent of 1000 high-definition films – in one five-minute pass over the ground station,” said Jade Wang, TBIRD program manager ( Jade Wang.
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